1. Field of the Invention
This invention relates to a device for supporting magnetic disk rotatably in a magnetic recording and playback apparatus.
2. Description of the Prior Art
A small magnetic disk having a diameter of, say, 3.5 inches usually has a central hub by which it is rotatably mounted on a disk supporting device in a magnetic recording and playback apparatus. The disk supporting device is typically of the construction as shown in FIGS. 5 and 6. It has in its center a shaft 1 to which an electric motor not shown is connected for rotating it clockwise as viewed in FIG. 5. A table 2 surrounds the shaft 1 and is secured thereto. The table 2 has an annular recess 2a at its top. An annular yoke 3 is secured to the bottom of the recess 2a and a rubber magnet 4 is secured to the yoke 3.
An annular leaf spring 5 is secured to the bottom of the table 2 by screws 6. A disk drive pin 7 is upstanding from the leaf spring 5 and extends through the table 2, the yoke 3 and the magnet 4. The pin 7 is located between the shaft 1 and the outer periphery of the table 2 and has an upper end exposed above the magnet 4. The yoke 3 has a projection which defines a stop 8 facing the pin 7 at a distance x therefrom. A slider 9 is fitted about the shaft 1 at the top of the table 2.
If a magnetic disk is placed on the device, its central hub, which is formed from a magnetic material, is attracted by the magnet 4. The pin 7 is pressed down by the hub, as the leaf spring 5 is deformed. The hub has a groove or hole. If the shaft 1 is rotated, the pin 7 is urged by the spring 5 to fit in the groove or hole of the hub and starts rotating the disk. The disk imparts a certain resistance to the rotation of the pin 7 and as a result, the pin 7 tends to incline. Such inclination is restricted by the stop 8.
The device as hereinabove described has a number of drawbacks as will hereunder be summarized.
(1) The job of assembling the device is inefficient, as separate steps are, for example, required for joining the yoke 3 and the leaf spring 5 to the opposite sides, respectively, of the table 2.
(2) Insofar as the yoke 3 and the leaf spring 5 are joined to the table 2 separately, the distance x between the pin 7 and the stop 8 is very likely to lack consistency due to possible inconsistencies in the manufacture or assembly of the yoke 3 or the spring 5. If the distance x is too large, the pin 7 is inclined to an undesirable extent when it is driving the disk. The undue inclination of the pin 7 gives rise to a reduction in accuracy of, for example, information recording on the disk. If the distance x is zero, i.e., if the pin 7 contacts the stop 8, the pin 7 fails to move up or down smoothly. In order to correct any such inconsistency of the distance x, it is necessary to loosen the screws 6 and adjust the position of the leaf spring 5 relative to the stop 8 after the device has once been assembled. This adjustment naturally complicates the job of manufacturing the device.
(3) The device is composed of an unreasonably large number of parts from the table 2 to the slider 9.